The present invention relates in general to systems and methods for cooling rack-mounted assemblages of individual electronics units, such as rack-mounted computer server units.
The power dissipation of integrated circuit chips, and the modules containing the chips, continue to increase in order to achieve increases in processor performance. This trend poses a cooling challenge at both the module and system level. Increased air flow rates are needed to effectively cool high power modules and to limit the temperature of the air that is exhausted into the computer center.
In many large server applications, processors along with their associated electronics (e.g. memory, disk drives, power, etc.) are packaged in removable drawer configurations stacked within a rack or frame. In other cases, the electronics may be in fixed locations within the rack or frame. Typically, the components are cooled by air moving in parallel air flow paths, usually front-to-back, impelled by one or more air moving devices (e.g., fans or blowers). In some cases it may be possible to handle increased power dissipation within a single drawer by providing greater air flow, through the use of a more powerful air moving device or by increasing the rotational speed (i.e. RPM) of an existing air moving device. However, this approach is becoming unmanageable at the frame level in the context of the computer installation (i.e. data center). The sensible heat load carried by the air exiting the frame will eventually exceed the ability of the room air conditioning to effectively handle the load. This is especially true for large installations with xe2x80x9cserver farmsxe2x80x9d or large banks of computer frames close together. In such installations not only will the room air conditioning be challenged, but the situation may also result in recirculation problems with some fraction of the xe2x80x9chotxe2x80x9d air exiting one frame being sucked into the air inlets of a nearby frame. Furthermore, while the acoustic noise level of a powerful (or higher RPM) air moving device in a single drawer may be within acceptable acoustic limits, because of the number of air moving devices in the frame, the total acoustic noise at the frame level may not be acceptable. In addition, the openings required in the frame for the entry and exit of air flow makes it difficult, if not impossible, to provide effective acoustic treatment to reduce the acoustic noise level outside the frame. Finally, as operating frequencies continue to increase, we are approaching the point where electromagnetic (EMC) cross talk between tightly spaced computer frames is becoming a problem largely due to the presence of the openings in the covers required for air flow.
Recently, there has been an attempt to address some of the defects noted above by combining the air cooling approach with an air-to-water heat exchanger fixed within the server cabinet below the frame electronics. An example of such a system is Sanmina""s EcoBay(trademark) 442. The present invention builds upon prior approaches in ways that will become apparent below.
For the foregoing reasons, therefore, there is a need in the art for an improved and self-contained mechanism for cooling rack-mounted modular electronic units. Objects of the present invention include providing such a mechanism, while addressing, for example, the acoustic and EMC constraints noted above.
The invention described here, which provides an air/liquid heat removal enclosure system with electromagnetic and acoustic noise control capability for electronic equipment, is an improvement over prior art systems. The invention utilizes an enclosure scheme within which a stack or stacks of electronic drawers are packaged. Air is circulated within the enclosure to cool the electronics and is passed across one or more air-to-liquid finned-tube heat exchanger(s) (mounted to the side of the electronics in a first embodiment, and in front and/or back of the electronics in a second embodiment) to transfer the total system heat load to water which then exits the frame. Because the frame is closed and because the inner walls are lined with sound absorbent or deadening material, much of the acoustic noise caused by the air moving devices will be contained within the closed cabinet. Also, since the cabinet is closed with only minimal openings at the bottom of the frame for cables, it will also exhibit improved characteristics with respect to reducing both susceptibility to electromagnetic interference from outside the cabinet and electromagnetic radiation from within the cabinet.
In one embodiment, the apparatus is described with a side-mounted air-to-liquid heat exchanger. In a second embodiment, the heat exchanger is in front of and/or behind the electronics and the air circulation is top to bottom, with a connecting duct in the bottom, a converging air flow supply plenum being formed in the front cover, a diverging air flow return plenum being formed in the back cover, with one or more optional air moving devices being located in the plenums; in a variant of the second embodiment, a connecting duct is in the top, with converging supply and diverging return air flow plenums; in yet another variant, connecting ducts are in both top and bottom and supply and return air flow plenums are doubly convergent and doubly divergent, respectively. Finally, a mechanism is described for automatically opening vent panels in the event of loss of coolant so that room air can be used for temporary cooling.
The recitation herein of desirable objects which are met by various embodiments of the present invention is not meant to imply or suggest that any or all of these objects are present as essential features, either individually or collectively, in the most general embodiment of the present invention or in any of its more specific embodiments.